With the beginning of the cutting and welding of the rear flange of the regulating valve of the bleaching tower of nitric acid unit in the fertilizer plant of Lanzhou Petrochemical Company, it marks that the overhaul of nitric acid unit in 2019 has been fully carried out.

As good at the maintenance of dynamic equipment maintenance of Lanzhou Petrochemical Weida Company a branch fitter class three, they opened the curtain of the overhaul. The Maintenance Branch 1 mainly undertakes the nitric acid unit "four-in-one" unit, which is manufactured by German MAN Company. The unit is composed of four compressors in series, including steam turbine, nitrogen oxide compressor, air compressor and tail gas expander. It is the key equipment for dilute nitrate production in nitric acid unit. In August 2016, the nitric acid unit was stopped for major overhaul, and the oil seal and radial tile of the unit were checked and cleaned. Since 2018, the nitrogen oxide compressor has been experiencing leakage in the center section, some bolts in the center section have been seriously corroded, and some oil seals of the unit have been leaking oil.

At the beginning of the overhaul, the company set construction period goals, safety goals, quality goals, environmental goals, civilized overhaul goals. From the overhaul of each link, all aspects of the detailed study and arrangement, in strict accordance with the implementation of various standards, do four "everything", that is, "everything has evidence to follow, everything has rules to follow, everything is responsible for, everything is supervised". The picture is April 15, Lanzhou Petrochemical Weida Company maintenance first branch fitter shift three staff to repair the unit. (Cao Ping Ren Kui)